Natural Rubber Processability and Abrasion Resistance via NMR Structural Control
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Solution Overview
Problem
Natural rubbers with high toluene-insoluble gel content have poor processability and require improved abrasion resistance for extended service life of rubber products like tires.
Innovation Solution
Development of natural rubbers characterized by specific 1H-NMR spectral peaks and structural unit ratios, which enhance processability and abrasion resistance, achieved through centrifugation and mixing of natural rubber latexes with different particle sizes, and incorporation in rubber compositions with specific carbon black and polybutadiene rubber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If natural rubber with high toluene-insoluble gel content is used, then abrasion resistance is improved, but processability deteriorates due to high Mooney viscosity
Solution Approach 1:
The invention changes the chemical structure parameter of natural rubber by controlling the ratio of specific structural units (formula c) to be 45 mol% or more, and controlling the sum of peak intensities at specific NMR frequencies to be 8.0 or less. This structural parameter change enables simultaneous achievement of good processability and abrasion resistance, resolving the contradiction between these two properties.
2Duration of action of stationary object
If natural rubber with high toluene-insoluble gel content is used, then service life is extended, but uniform dispersion of compounding agents deteriorates due to high Mooney viscosity
Solution Approach 1:
The invention modifies the molecular structure parameter of natural rubber by ensuring that structural units of formula (c) constitute 45 mol% or more of the total. This structural modification reduces Mooney viscosity while maintaining high gel content, thereby enabling uniform dispersion of compounding agents during kneading while preserving the extended service life.
3Ease of manufacture
If conventional natural rubber is used, then production is simpler, but abrasion resistance is insufficient for extended service life
Solution Approach 1:
The invention specifies precise structural parameters of natural rubber: the sum of peak intensities at 4.17, 3.94, 3.84, 3.73, 3.50, and 3.41 ppm (normalized to 10,000 for the peak at 5.11 ppm) must be 8.0 or less, and structural units of formula (c) must be 45 mol% or more. These parameter specifications enable identification of natural rubber with both good processability and superior abrasion resistance.
Solution Approach 2:
The invention creates a composite rubber composition by combining the specifically structured natural rubber with carbon black (20-60 parts by mass per 100 parts rubber) and polybutadiene rubber (10-40 parts by mass per 100 parts rubber). This composite formulation enhances abrasion resistance while maintaining production feasibility.
Data Source
AI summary
The invention provides natural rubbers having improved processability and/or abrasion resistance, rubber compositions containing the natural rubbers, and pneumatic tires formed from the rubber compositions. The invention relates to a natural rubber which shows a 1H-NMR spectrum where the sum of peak intensities at about 4.17, 3.94, 3.84, 3.73, 3.50, and 3.41 ppm, normalized to 10,000 for the peak intensity at about 5.11 ppm, is 8.0 or less.